Contractile and vasorelaxant effects of hydrogen sulfide and its biosynthesis in the human internal mammary artery

Involvement of different K+ channel subtypes in hydrogen sulfide-induced vasorelaxation of human internal mammary artery

BACKGROUND

Changes in K+ channel expression/function are associated with disruption of vascular reactivity in several pathological conditions, including hypertension, diabetes, and atherosclerosis. Gasotransmitters achieve part of their effects in the organism by regulating ion channels, especially K+ channels. Their involvement in hydrogen sulfide (H2S)-mediated vasorelaxation is still unclear, and data about human vessels are limited.

OBJECTIVE

To determine the role of K+ channel subtypes in the vasorelaxant mechanism of H2S donor, sodium-hydrosulfide (NaHS), on isolated human internal mammary artery (HIMA).

RESULTS

NaHS (1 × 10-6-3 × 10-3 mol/L) induced a concentration-dependent relaxation of HIMA pre-contracted by phenylephrine and high K+. Among K+ channel blockers, iberiotoxin, glibenclamide, 4-aminopyridine (4-AP), and margatoxin significantly inhibited NaHS-induced relaxation of phenylephrine-contracted HIMA (P < 0.01), whereas in the presence of apamin/1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34) combination, the HIMA relaxation was partially reduced (P < 0.05). The effect of NaHS was antagonized by NO pathway inhibitors, L-NAME and KT5823, and by cyclo-oxygenase inhibitor, indomethacin (P < 0.01). Under conditions of blocked NO/prostacyclin synthesis and release, apamin/TRAM-34 and glibenclamide caused further decrease in NaHS-induced vasorelaxation (P < 0.01), while iberiotoxin, 4-AP, and margatoxin were without additional effect (P > 0.05). In the presence of nifedipine, NaHS induced partial relaxation of HIMA (P < 0.01).

CONCLUSION

Our results demonstrated that H2S donor, NaHS, induced concentration-dependent relaxation of isolated HIMA. Vasorelaxant mechanisms of H2S included direct or indirect opening of different K+ channel subtypes, KATP, BKCa, SKCa/IKCa, and KV (subtype KV1.3), in addition to NO pathway activation and interference with extracellular Ca2+ influx.

Inhibition of cystathionine-gamma lyase dampens vasoconstriction in mouse and human intracerebral arterioles

AIM

In extracerebral vascular beds cystathionine-gamma lyase (CSE) activity plays a vasodilatory role but the role of this hydrogen sulfide (H2 S) producing enzyme in the intracerebral arterioles remain poorly understood. We hypothesized a similar function in the intracerebral arterioles.

METHODS

Intracerebral arterioles were isolated from wild type C57BL/6J mouse (9-12 months old) brains and from human brain biopsies. The function (contractility and secondary dilatation) of the intracerebral arterioles was tested ex vivo by pressure myography using a perfusion set-up. Reverse transcription polymerase chain reaction was used for detecting CSE expression.

RESULTS

CSE is expressed in human and mouse intracerebral arterioles. CSE inhibition with L-propargylglycine (PAG) significantly dampened the K+ -induced vasoconstriction in intracerebral arterioles of both species (% of maximum contraction: in human control: 45.4 ± 2.7 versus PAG: 27 ± 5.2 and in mouse control: 50 ± 1.5 versus PAG: 33 ± 5.2) but did not affect the secondary dilatation. This effect of PAG was significantly reversed by the H2 S donor sodium hydrosulfide (NaSH) in human (PAG + NaSH: 38.8 ± 7.2) and mouse (PAG + NaSH: 41.7 ± 3.1) arterioles, respectively. The endothelial NO synthase (eNOS) inhibitor, Nω-Nitro-l-arginine methyl ester (L-NAME), and the inhibitor of soluble guanylate cyclase (sGC), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) reversed the effect of PAG on the K+ -induced vasoconstriction in the mouse arterioles and attenuated the K+ -induced secondary dilatation significantly.

CONCLUSION

CSE contributes to the K+ -induced vasoconstriction via a mechanism involving H2 S, eNOS, and sGC whereas the secondary dilatation is regulated by eNOS and sGC but not by CSE.

DHA, RvD1, RvD5, and MaR1 reduce human coronary arteries contractions induced by PGE2

In patients with coronary artery disease (CAD), plasma levels of pro-inflammatory lipid mediators such as PGE₂ and TxA₂ are increased. They could increase vascular contraction while EPA and DHA could reduce it. Studies have been mostly conducted on animal vessels. Therefore, the aim of the study was to investigate if EPA, DHA, and DHA-derived metabolites: RvD1, RvD5 and MaR1 can modulate contraction of human coronary arteries (HCA) induced by PGE₂ or TxA₂ stable analogue (U46619). DHA and EPA relaxed HCA pre-contracted with PGE₂. 18 h-incubation with DHA but not EPA reduced the PGE₂-induced contractions. Pre-incubation with RvD1, RvD5 and MaR1 reduced the PGE₂-induced contractions. Indomethacin did not significantly modify the PGE₂ responses. L-NOARG (inhibitor of nitric oxide synthase), reduced only the PGE₂-induced contractions in RvD1-treated rings. Finally, FPR2/ALX, GPR32 and LGR6 receptors are detected in HCA by immunofluorescence. Our results indicate that DHA and its metabolites could be beneficial for HCA blood flow and could be a therapeutic perspective for patients with CAD.

Endothelial dysfunction: developmental mechanisms and therapeutic strategies

Introduction: Every year the importance of the normal functioning of the endothelial layer of the vascular wall in maintaining the health of the body becomes more and more obvious.

The physiological role of the endothelium: The endothelium is a metabolically active organ actively involved in the regulation of hemostasis, modulation of inflammation, maintenance of hemovascular homeostasis, regulation of angiogenesis, vascular tone, and permeability.

Risk factors for the development of endothelial dysfunction: Currently, insufficient bioavailability of nitric oxide is considered the most significant risk factor for endothelial dysfunction.

Mechanisms of development of endothelial dysfunction: The genesis of endothelial dysfunction is a multifactorial process. Among various complex mechanisms, this review examines oxidative stress, inflammation, hyperglycemia, vitamin D deficiency, dyslipidemia, excess visceral fat, hyperhomocysteinemia, hyperuricemia, as well as primary genetic defect of endotheliocytes, as the most common causes in the population underlying the development of endothelial dysfunction.

Markers of endothelial dysfunction in various diseases: This article discusses the main biomarkers of endothelial dysfunction currently used, as well as promising biomarkers in the future for laboratory diagnosis of this pathology.

Therapeutic strategies: Therapeutic approaches to the endothelium in order to prevent or reduce a degree of damage to the vascular wall are briefly described.

Conclusion: Endothelial dysfunction is a typical pathological process involved in the pathogenesis of many diseases. Thus, pharmacological agents with endothelioprotective properties can provide more therapeutic benefits than a drug without such an effect.

Hydrogen Sulfide Metabolizing Enzymes in the Intestinal Mucosa in Pediatric and Adult Inflammatory Bowel Disease

Hydrogen sulfide (H2S) is a toxic gas that has important regulatory functions. In the colon, H2S can be produced and detoxified endogenously. Both too little and too much H2S exposure are associated with inflammatory bowel disease (IBD), a chronic intestinal disease mainly classified as Crohn's disease (CD) and ulcerative colitis (UC). As the pathogenesis of IBD remains elusive, this study's aim was to investigate potential differences in the expression of H2S-metabolizing enzymes in normal aging and IBD. Intestinal mucosal biopsies of 25 adults and 22 children with IBD along with those of 26 healthy controls were stained immunohistochemically for cystathionine-γ-lyase (CSE), 3-mercapto-sulfurtransferase (3-MST), ethylmalonic encephalopathy 1 protein (ETHE1), sulfide:quinone oxidoreductase (SQOR) and thiosulfate sulfurtransferase (TST). Expression levels were calculated by multiplication of the staining intensity and percentage of positively stained cells. Healthy adults showed an overall trend towards lower expression of H2S-metabolizing enzymes than healthy children. Adults with IBD also tended to have lower expression compared to controls. A similar trend was seen in the enzyme expression of children with IBD compared to controls. These results indicate an age-related decrease in the expression of H2S-metabolizing enzymes and a dysfunctional H2S metabolism in IBD, which was less pronounced in children.

Prophylactic Treatment with Hydrogen Sulphide Can Prevent Renal Ischemia-Reperfusion Injury in L-NAME Induced Hypertensive Rats with Cisplatin-Induced Acute Renal Failure

(Background and Objectives): Renal ischemia perfusion injury is one of the major issues in kidney transplant. The aim of the study was to investigate the hypothesis that prophylactic treatment-with a hydrogen sulphide donor to an acute renal failure case of hypertensive rats-can minimize the ischemia reperfusion injury of the kidney which is beneficial for kidney transplant. To check this hypothesis, the present study was designed to investigate the effect of chronic administration of a hydrogen sulphide (H2S) donor and sodium hydrosulfide (NaHS) on nuclear factor kappa B (NF-kB) and inter cellular adhesion molecule-1 (ICAM-1) concentration in non-renal failure (NRF) and acute renal failure (ARF) rats in the ischemia-reperfusion injury (IRI) model of the kidney in both normotensive WKY and hypertensive rats (L-nitro arginine methyl ester (L-NAME-induced); (Materials and Methods): A total number of 48 Sprague-Dawley rats were recruited into eight groups each consisting of six animals. Each of these eight groups was used to measure systemic and renal parameters, H2S, antioxidant parameters in plasma, plasma concentration of NF-kB and ICAM-1 and renal cortical blood pressure. ARF was induced by single intraperitoneal (i.p.) cisplatin injection (5 mg/kg). Hypertension was induced by oral administration of L-NAME in drinking water for four weeks at 40 mg/kg/day. NaHS was administered (i.p) at 56 µmol/kg for five weeks while dL-propargylglycine (PAG), a H2S generation inhibitor, was administered as a single intra-peritoneal injection (50 mg/kg). An acute surgical experiment was performed for the induction of renal ischemia for 30 min by renal artery clamping followed by reperfusion for three hours; (Results): Chronic administration of NaHS attenuated the severity of ARF in both normotensive and hypertensive animals (L-NAME) along with lowering the blood pressure in hypertensive groups. NaHS improved the oxidative stress parameters such as total superoxide dismutase (T-SOD), glutathione (GSH) and reduced the malondialdehyde (MDA) concentration along with reduction of NF-kB and ICAM-1 following renal IRI; Conclusions: These findings demonstrate that H2S not only reduced the severity of cisplatin induced ARF but also reduced the severity of renal IRI by upregulating antioxidants along with decreased concentrations of NF-kB and ICAM-1 in normotensive and L-NAME induced hypertensive rats.

The Role of Perivascular Adipose Tissue-Derived Hydrogen Sulfide in the Control of Vascular Homeostasis

Significance: Emerging evidence suggests that perivascular adipose tissue (PVAT) has a relevant role in the control of vascular tone in physiology and pathology. Healthy PVAT has anticontractile, anti-inflammatory, and antioxidative actions. Accumulating data from both human and experimental animal models indicate that PVAT dysfunction is conceivably coupled to cardiovascular diseases, and it is associated with vascular inflammation, oxidative stress, and arterial remodeling. Therefore, "healthy" PVAT may constitute a novel therapeutic target for the prevention and treatment of cardiovascular diseases. Recent Advances: Hydrogen sulfide (H₂S) has been recognized as a vascular anti-contractile factor released from PVAT. The enzymes deputed to H₂S biosynthesis are variously expressed in PVAT and strictly dependent on the vascular bed and species. Metabolic and cardiovascular diseases can alter the morphological and secretory characteristics of PVAT, influencing also the H₂S signaling. Here, we discuss the role of PVAT-derived H₂S in healthy conditions and its relevance in alterations occurring in vascular disorders. Critical Issues: We discuss how a better understanding may help in the prevention of vascular dysfunction related to alteration in PVAT-released H₂S as well as the importance of the interplay between PVAT and H₂S. Future Directions: We propose future directions to evaluate the contribution of each enzyme involved in H₂S biosynthesis and their alteration/switch occurring in vascular disorders and the remaining challenges in investigating the role of H₂S. Antioxid. Redox Signal. 37, 84-97.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Hydrogen sulfide-induced post-translational modification as a potential drug target

Hydrogen sulfide (H₂S) is one of the three known gas signal transducers, and since its potential physiological role was reported, the literature on H₂S has been increasing. H₂S is involved in processes such as vasodilation, neurotransmission, angiogenesis, inflammation, and the prevention of ischemia-reperfusion injury, and its mechanism remains to be further studied. At present, the role of post-translational processing of proteins has been considered as a possible mechanism for the involvement of H₂S in a variety of physiological processes. Current studies have shown that H₂S is involved in S-sulfhydration, phosphorylation, and S-nitrosylation of proteins, etc. This paper focuses on the effects of protein modification involving H₂S on physiological and pathological processes, looking forward to providing guidance for subsequent research.

Hydrogen Sulphide Treatment Prevents Renal Ischemia-Reperfusion Injury by Inhibiting the Expression of ICAM-1 and NF-kB Concentration in Normotensive and Hypertensive Rats

Our main objective was to investigate the effect of chronic administration of hydrogen sulphide donor (sodium hydrosulphide) on the expression of intercellular adhesion molecule-1 (ICAM-1) and concentration of nuclear factor-kappa B (NF-kB) in a renal ischemia-reperfusion injury (IRI) model of WKY and L-nitro-arginine-methyl-ester (L-NAME)-induced hypertensive rats. Sodium hydrosulphide (NaHS) was administered intraperitoneally (i.p.) for 35 days while cystathionine gamma lyase (CSE) inhibitor dL-propargylglycine (PAG) was administered at a single dose of 50 mg/kg. Animals were anesthetised using sodium pentobarbitone (60 mg/kg) and then prepared to induce renal ischemia by clamping the left renal artery for 30 min followed by 3 h of reperfusion. Pre-treatment with NaHS improved the renal functional parameters in both WKY and L-NAME-induced hypertensive rats along with reduction of blood pressure in hypertensive groups. Oxidative stress markers like malondialdehyde (MDA), total superoxide dismutase (T-SOD) and glutathione (GSH) were also improved by NaHS treatment following renal IRI. Levels of ICAM-1 and NF-kB concentration were reduced by chronic treatment with NaHS and increased by PAG administration after renal IRI in plasma and kidney. Treatment with NaHS improved tubular morphology and glomerulus hypertrophy. Pre-treatment with NaHS reduced the degree of renal IRI by potentiating its antioxidant and anti-inflammatory mechanism, as evidenced by decreased NF-kB concentration and downregulation of ICAM-1 expression.

Involvement of 3',5'-cyclic inosine monophosphate in cystathionine γ-lyase-dependent regulation of the vascular tone

BACKGROUND AND PURPOSE

l-cysteine or hydrogen sulfide (H₂ S) donors induce a biphasic effect on precontracted isolated vessels. The contractile effect occurs within a concentration range of 10 nM to 3 μM followed by vasodilatation at 30-100 μM. Here, we have investigated the signalling involved in the H₂ S-induced contraction.

EXPERIMENTAL APPROACH

Vascular response to NaHS or l-cysteine is evaluated on isolated precontracted with phenylephrine vessel rings harvested from wild type, cystathionine γ-lyase (CSE^-/- ), soluble guanylyl cyclase (sGC_α1 ^-/- ) and endothelial nitric oxide synthase (eNOS^-/- ) knock-out mice. The cAMP, cGMP and inosine 3',5'-cyclic monophosphate (cIMP) levels are simultaneously quantified using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis. The involvement of sGC, phosphodiesterase (PDE) 4A and PDE5 are also evaluated.

KEY RESULTS

CSE-derived H₂ S-induced contraction requires an intact eNOS/NO/sGC pathway and involves cIMP as a second messenger. H₂ S contractile effect involves a transient increase of cGMP and cAMP metabolism caused by PDE5 and PDE4A, thus unmasking cIMP contracting action. The stable cell-permeable analogue of cIMP elicits concentration-dependent contraction on a stable background tone induced by phenylephrine. The lack of cIMP, coupled to the hypocontractility displayed by vessels harvested from CSE^-/- mice, confirms that H₂ S-induced contraction involves cIMP.

CONCLUSION AND IMPLICATIONS

The endothelium dynamically regulates vessel homeostasis by modulating contractile tone. This also involves CSE-derived H₂ S that is mediated by cIMP.

GYY4137 and Sodium Hydrogen Sulfide Relaxations Are Inhibited by L-Cysteine and KV7 Channel Blockers in Rat Small Mesenteric Arteries

Donors of H₂S may be beneficial in treating cardiovascular diseases where the plasma levels of H₂S are decreased. Therefore, we investigated the mechanisms involved in relaxation of small arteries induced by GYY4137 [(4-methoxyphenyl)-morpholin-4-yl-sulfanylidene-sulfido-λ5-phosphane;morpholin-4-ium], which is considered a slow-releasing H₂S donor. Sulfides were measured by use of 5,5′-dithiobis-(2-nitro benzoic acid), and small rat mesenteric arteries with internal diameters of 200–250 µm were mounted in microvascular myographs for isometric tension recordings. GYY4137 produced similar low levels of sulfides in the absence and the presence of arteries. In U46619-contracted small mesenteric arteries, GYY4137 (10⁻⁶–10^–3 M) induced concentration-dependent relaxations, while a synthetic, sulfur-free, GYY4137 did not change the vascular tone. L-cysteine (10⁻⁶–10^–3 M) induced only small relaxations reaching 24 ± 6% at 10^–3 M. Premixing L-cysteine (10^–3 M) with Na₂S and GYY4137 decreased Na₂S relaxation and abolished GYY4137 relaxation, an effect prevented by an nitric oxide (NO) synthase inhibitor, L-NAME (N^ω-nitro-L-arginine methyl ester). In arteries without endothelium or in the presence of L-NAME, relaxation curves for GYY4137 were rightward shifted. High extracellular K⁺ concentrations decreased Na₂S and abolished GYY4137 relaxation suggesting potassium channel-independent mechanisms are also involved Na₂S relaxation while potassium channel activation is pivotal for GYY4137 relaxation in small arteries. Blockers of large-conductance calcium-activated (BK_Ca) and voltage-gated type 7 (K_V7) potassium channels also inhibited GYY4137 relaxations. The present findings suggest that L-cysteine by reaction with Na₂S and GYY4137 and formation of sulfides, inhibits relaxations by these compounds. The low rate of release of H₂S species from GYY4137 is reflected by the different sensitivity of these relaxations towards high K⁺ concentration and potassium channel blockers compared with Na₂S. The perspective is that the rate of release of sulfides plays an important for the effects of H₂S salt vs. donors in small arteries, and hence for a beneficial effect of GYY4137 for treatment of cardiovascular disease.

Mechanisms underlying the vasorelaxant effect of hydrogen sulfide on human saphenous vein

Hydrogen sulfide (H₂ S) represents the third and the youngest member of the gaseous transmitters family. The dominant effect of H₂ S on isolated vessels is vasodilation. As the mechanism of H₂ S-induced relaxation in human vessels remains unclear, the present study aimed to investigate the effects of H₂ S donor, sodium hydrosulfide (NaHS), on isolated human saphenous vein (HSV) and to determine the mechanism of action. Our results showed that NaHS (1 µM-3 mM) induced a concentration-dependent relaxation of endothelium-intact HSV rings pre-contracted by phenylephrine. Pre-treatment with L-NAME, ODQ and KT5823 significantly inhibited NaHS-induced relaxation, while indomethacin induced partial inhibition. Among K⁺ channel blockers, the combination of apamin and TRAM-34 significantly affected the relaxation produced by NaHS, while iberiotoxin and glibenclamide only reduced maximal relaxation of HSV. NaHS partially relaxed endothelium-intact rings pre-contracted by high K⁺ , as well as phenylephrine-contracted rings in the presence of nifedipine. Additionally, the incubation of HSV rings with NaHS increased NO production. These results demonstrate that NaHS produces the concentration- and endothelium-dependent relaxation of isolated HSV. Vasorelaxation to NaHS probably involves activation of NO/cGMP/PKG pathway and partially prostacyclin. In addition, different K⁺ channels subtypes, especially SK_Ca and IK_Ca , as well as BK_Ca and K_ATP channels in high concentrations of NaHS, probably participate in the NaHS-induced vasorelaxation.

Fetal Hypothyroidism Impairs Aortic Vasorelaxation Responses in Adulthood: Involvement of Hydrogen Sulfide and Nitric Oxide Cross talk

ABSTRACT

Thyroid hormones have a wide range of effects on growth, differentiation, evolution, metabolism, and physiological function of all tissues, including the vascular bed. In this study, the effect of fetal hypothyroidism on impairment of aortic vasorelaxation responses in adulthood was investigated with emphasis on possible involvement of hydrogen sulfide (H2S)/nitric oxide interaction. Two groups of female rats were selected. After mating and observation of vaginal plaque, one group received propylthiouracil (200 ppm in drinking water) until the end of pregnancy and another group had no propylthiouracil treatment during the fetal period. In adult rats, aortic relaxation responses to l-arginine and GYY4137 were assessed in the presence or absence of Nω-nitro-L-arginine methyl ester hydrochloride and dl-propargylglycine in addition to the biochemical measurement of thyroid hormones and some related factors. Obtained findings showed a lower vasorelaxation response for GYY4137 and l-arginine in the fetal hypothyroidism group, and preincubation with Nω-nitro-L-arginine methyl ester hydrochloride or dl-propargylglycine did not significantly aggravate this weakened relaxation response. In addition, aortic levels of sirtuin 3, endothelial nitric oxide synthase, cystathionine gamma-lyase, and H2S were significantly lower in the fetal hypothyroidism group. Meanwhile, no significant changes were obtained regarding serum levels of thyroid hormones including free triiodothyronine;, total triiodothyronine, free thyroxine, total thyroxine, and thyroid-stimulating hormone in adult rats. It can be concluded that hypothyroidism in the fetal period has inappropriate effects on the differentiation and development of vascular bed with subsequent functional abnormality that persists into adulthood, and part of this vascular abnormality is mediated through weakened interaction and/or cross talk between H2S and nitric oxide.

Acute acrylonitrile exposure inhibits endogenous H2S biosynthesis in rat brain and liver: The role of CBS/3-MPST-H2S pathway in its astrocytic toxicity

Hydrogen sulfide (H₂S) as the third gasotransmitter molecule serves various biological regulatory roles in health and disease. Acrylonitrile (AN) is a common occupational toxicant and environmental pollutant, causing brain and liver damage in mammals. The biotransformation of AN is dependent-upon reduced glutathione (GSH), cysteine and other sulfur-containing compounds. However, the effects of AN on the endogenous H₂S biosynthesis pathway have yet to be determined. Herein, we demonstrated that a single exposure to AN (at 25, 50, or 75 mg/kg for 1, 6 or 24 h) decreased the endogenous H₂S content and H₂S-producing capacity in a dose-dependent manner, both in the cerebral cortex and liver of rats in vivo. In addition, the inhibitory effects of AN (1, 2.5, 5, 10 mM for 12 h) on the H₂S content and/or the expression of H₂S-producing enzymes were also found both in primary rat astrocytes and rat liver cell line (BRL cells). Impairment in the H₂S biosynthesis pathway was also assessed in primary rat astrocytes treated with AN. It was found that inhibition of the cystathionine-β-synthase (CBS)/3-mercaptopyruvate sulfurtransferase (3-MPST)-H₂S pathway with the CBS inhibitor or 3-MPST-targeted siRNA significantly increased the AN-induced (5 mM for 12 h) cytotoxicity in astrocytes. In turn, CBS activation or 3-MPST overexpression as well as exogenous NaHS supplementation significantly attenuated AN-induced cytotoxicity. Taken together, endogenous H₂S biosynthesis pathway was disrupted in rats acutely exposed to AN, which contributes to acute AN neurotoxicity in primary rat astrocytes.

The vasodilatory mechanism of nitric oxide and hydrogen sulfide in the human mesenteric artery in patients with colorectal cancer

Recent studies have focused on the role of gasotransmitters in cancer progression and prevention. Therefore, the current study was designed to explore the vasodilator activity of NO and H₂S in the human mesenteric arteries of patients with colorectal cancer (CRC) via the activation of K⁺ channels. A total of two sets of experiments were established for the current investigation. Blood samples from patients with CRC were obtained to detect serum levels of endocan and malondialdehyde (MDA). The role of K⁺ channels in mediating the vasodilation of the human mesenteric artery in response to sodium nitroprusside (SNP) and sodium disulfide (Na₂S) was assessed. The level of serum endocan was indicated to be decreased in patients with CRC compared with healthy individuals, while the level of serum MDA remained unaltered between groups. The arterial rings pre-contracted with norepinephrine were first relaxed by the cumulative addition of increasing concentrations of either SNP (30 nM-30 µM) or (1-6 mM). Maximal relaxation rates were then calculated at 15 min intervals for 60 min. Pre-incubation of arterial rings for 20 min with individual K⁺ channel blockers was indicated to significantly reduce SNP- and Na₂S-induced relaxation at different time points. Pre-treatment of L-nitro-arginine methyl ester did not alter vasodilation that was induced by Na₂S. Furthermore, vasodilation of the CRC mesenteric artery was not altered by the synergistic application of SNP and Na₂S, while pre-incubation of arterial rings with D,L-propargylglycine significantly enhanced vasodilation induced by SNP. These results indicated that endothelial dysfunction and oxidative stress do not serve roles in the pathogenesis of CRC. The dilatory mechanisms of NO and H₂S in mesenteric arteries of patients with CRC were K⁺ channel- and time-dependent, and the activity of cystathionine γ-lyase enzyme inhibited the ability of exogenous NO in vasodilation processes.

Potential role of hydrogen sulfide in diabetes-impaired angiogenesis and ischemic tissue repair

Diabetes is one of the most prevalent metabolic disorders and is estimated to affect 400 million of 4.4% of population worldwide in the next 20 year. In diabetes, risk to develop vascular diseases is two-to four-fold increased. Ischemic tissue injury, such as refractory wounds and critical ischemic limb (CLI) are major ischemic vascular complications in diabetic patients where oxygen supplement is insufficient due to impaired angiogenesis/neovascularization. In spite of intensive studies, the underlying mechanisms of diabetes-impaired ischemic tissue injury remain incompletely understood. Hydrogen sulfide (H₂S) has been considered as a third gasotransmitter regulating angiogenesis under physiological and ischemic conditions. Here, the underlying mechanisms of insufficient H₂S-impaired angiogenesis and ischemic tissue repair in diabetes are discussed. We will primarily focuses on the signaling pathways of H₂S in controlling endothelial function/biology, angiogenesis and ischemic tissue repair in diabetic animal models. We summarized that H₂S plays an important role in maintaining endothelial function/biology and angiogenic property in diabetes. We demonstrated that exogenous H₂S may be a theraputic agent for endothelial dysfunction and impaired ischemic tissue repair in diabetes.

The Interaction of the Endogenous Hydrogen Sulfide and Oxytocin Systems in Fluid Regulation and the Cardiovascular System

The purpose of this review is to explore the parallel roles and interaction of hydrogen sulfide (H2S) and oxytocin (OT) in cardiovascular regulation and fluid homeostasis. Their interaction has been recently reported to be relevant during physical and psychological trauma. However, literature reports on H2S in physical trauma and OT in psychological trauma are abundant, whereas available information regarding H2S in psychological trauma and OT in physical trauma is much more limited. This review summarizes recent direct and indirect evidence of the interaction of the two systems and their convergence in downstream nitric oxide-dependent signaling pathways during various types of trauma, in an effort to better understand biological correlates of psychosomatic interdependencies.

Hydrogen sulphide-releasing aspirin enhances cell capabilities of anti-oxidative lesions and anti-inflammation

Hydrogen sulphide (H₂S) has been considered as a toxic gas for a long time till new researches discovered the endogenous H₂S effects on physiological and pathological processes. In virtue of H₂S’s effects on cellular redox imbalance and aspirin’s good anticoagulation property, exogenous H₂S donors, such as H₂S-releasing aspirin (ACS14), have been explored to attenuate side effects of aspirin on gastrointestinal mucosal damage. However, existing researches mainly focus on the antithrombotic effects. Considering H₂S role in angiogenesis and vascular-protection progress, we herein focused on if ACS14 further has the ability to attenuate oxidative lesion and inflammation in human umbilical vein endothelial cells (HUVECs) and macrophages. In this study, we synthesized ACS14 by 5-(4-methoxyphenyl)-1,2-dithiole-3-thione and o-acetylsalicylic acid (aspirin), and the obtained compounds showed the ability to release H₂S. Our data illustrated that both aspirin and ACS14 had good cytocompatibility, and could support the proliferation of HUVECs. And, ACS14 was found to be able to promote 1.6 folds increase compared to aspirin. H₂S released from ACS14 was detected inside cells, wherein H2S fluorescence intensity increased twofold in 5 μM and 10 μM ACS14 groups than 1 μM group. Owing to reactive oxygen species inside cells being obviously decreased in ACS14 group, the apoptosis rate of HUVEC herein was reduced as low as 1.6% from 60% of blank group. Meanwhile, the tumour necrosis factor alpha release in macrophage was also declined by 15% in ACS14 groups than the others. Basically, the ACS14 we obtained had the cyto-protective and anti-inflammatory capabilities. Potential applications for vascular intima repair in atherosclerosis are further expected.

Role of Endothelial Dysfunction in Cardiovascular Diseases: The Link Between Inflammation and Hydrogen Sulfide

Endothelial cells are important constituents of blood vessels that play critical roles in cardiovascular homeostasis by regulating blood fluidity and fibrinolysis, vascular tone, angiogenesis, monocyte/leukocyte adhesion, and platelet aggregation. The normal vascular endothelium is taken as a gatekeeper of cardiovascular health, whereas abnormality of vascular endothelium is a major contributor to a plethora of cardiovascular ailments, such as atherosclerosis, aging, hypertension, obesity, and diabetes. Endothelial dysfunction is characterized by imbalanced vasodilation and vasoconstriction, elevated reactive oxygen species (ROS), and proinflammatory factors, as well as deficiency of nitric oxide (NO) bioavailability. The occurrence of endothelial dysfunction disrupts the endothelial barrier permeability that is a part of inflammatory response in the development of cardiovascular diseases. As such, abrogation of endothelial cell activation/inflammation is of clinical relevance. Recently, hydrogen sulfide (H₂S), an entry as a gasotransmitter, exerts diverse biological effects through acting on various targeted signaling pathways. Within the cardiovascular system, the formation of H₂S is detected in smooth muscle cells, vascular endothelial cells, and cardiomyocytes. Disrupted H₂S bioavailability is postulated to be a new indicator for endothelial cell inflammation and its associated endothelial dysfunction. In this review, we will summarize recent advances about the roles of H₂S in endothelial cell homeostasis, especially under pathological conditions, and discuss its putative therapeutic applications in endothelial inflammation-associated cardiovascular disorders.

Role of Hydrogen Sulfide in Chronic Diseases

In the past, hydrogen sulfide (H₂S) was considered as a poisonous gas or waste of the body. Later, researchers found that H₂S-producing enzymes exist in mammals. Moreover, their findings indicated that endogenous H₂S was associated with the occurrence of many diseases. Therefore, endogenous H₂S is able to participate in the regulation of physiological and pathological functions of the body as a gas signaling molecule. In this review, we summarize the regulation mechanism of endogenous H₂S on the body, such as proliferation, apoptosis, migration, angiogenesis, as well as vasodilation/vasoconstriction. Furthermore, we also analyze the relationship between H₂S and some chronic diseases, including hypoxic pulmonary hypertension, myocardial infarction, ischemic perfusion kidney injury, diabetes, and chronic intestinal diseases. Finally, we discuss dietary restriction and drugs that target for H₂S. Hence, H₂S is expected to become a potential target for treatment of these chronic diseases.

The role of gasotransmitters in neonatal physiology

The gasotransmitters, nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO), are endogenously-produced volatile molecules that perform signaling functions throughout the body. In biological tissues, these small, lipid-permeable molecules exist in free gaseous form for only seconds or less, and thus they are ideal for paracrine signaling that can be controlled rapidly by changes in their rates of production or consumption. In addition, tissue concentrations of the gasotransmitters are influenced by fluctuations in the level of O₂ and reactive oxygen species (ROS). The normal transition from fetus to newborn involves a several-fold increase in tissue O₂ tensions and ROS, and requires rapid morphological and functional adaptations to the extrauterine environment. This review summarizes the role of gasotransmitters as it pertains to newborn physiology. Particular focus is given to the vasculature, ventilatory, and gastrointestinal systems, each of which uniquely illustrate the function of gasotransmitters in the birth transition and newborn periods. Moreover, given the relative lack of studies on the role that gasotransmitters play in the newborn, particularly that of H₂S and CO, important gaps in knowledge are highlighted throughout the review.

Vasorelaxation elicited by endogenous and exogenous hydrogen sulfide in mouse mesenteric arteries

H₂S causes vasorelaxation however there is considerable heterogeneity in the reported pharmacological mechanism of this effect. This study examines the contribution of endogenously released H₂S in the regulation of vascular tone and the mechanism of H₂S-induced vasorelaxation in small resistance-like arteries. Mesenteric arteries from C57 and eNOS^-/- mice were mounted in myographs to record isometric force. Vasorelaxation responses to NaHS were examined in the presence of various inhibitors of vasorelaxation pathways. Expression and activity of the H₂S-producing enzyme, cystathionine-γ-lyase (CSE), were also examined. CSE was expressed in vascular smooth muscle and perivascular adipose cells from mouse mesenteric artery. The substrate for CSE, L-cysteine, caused a modest vasorelaxation (35%) in arteries from C57 mice and poor vasorelaxation (10%) in arteries from eNOS^-/- mice that was sensitive to the CSE inhibitor DL-propargylglycine. The fast H₂S donor, NaHS, elicited a full and biphasic vasorelaxation response in mesenteric arteries (EC₅₀ (1) 8.7 μM, EC₅₀ (2) 0.6 mM), which was significantly inhibited in eNOS^-/- vessels (P < 0.05), unaffected by endothelial removal, or blockers at any point in the NO via soluble guanylate cyclase and cGMP (NO-sGC-cGMP) vasorelaxation pathway. Vasorelaxation to NaHS was significantly inhibited by blocking K⁺ channels of the K_Ca and K_V subtypes and the Cl^-/HCO₃^- exchanger (P < 0.05). Further experiments showed that NaHS can significantly inhibit voltage-gated Ca²⁺ channel function (P < 0.05). The vasorelaxant effect of H₂S in small resistance-like arteries is complex, involving eNOS, K⁺ channels, Cl^-/HCO₃^- exchanger, and voltage-gated Ca²⁺ channels. CSE is present in the smooth muscle and periadventitial adipose tissue of these resistance-like vessels and can be activated to cause modest vasorelaxation under these in vitro conditions.

Hydrogen sulfide-mediated endothelial function and the interaction with eNOS and PDE5A activity in human internal mammary arteries

Objective

To investigate the role of hydrogen sulfide (H2S) in human internal mammary arteries (IMA) and its interaction with endothelial nitric oxide synthase (eNOS) and phosphodiesterase (PDE)5A activity.

Methods

Human IMA segments from patients undergoing coronary artery bypass grafting (CABG) were studied by myography for acetylcholine and sodium hydrosulfide (NaHS)-induced relaxation. Locations of 3-mercaptopyruvate sulfurtransferase (3-MPST) and cysteine aminotransferase (CAT) were examined immunohistochemically. Levels of H2S, eNOS, phosphorylated-eNOSser1177, and PDE5A were measured.

Results

In IMA segments from 47 patients, acetylcholine-induced relaxation (resistant to NG-nitro-L-arginine and indomethacin) was significantly attenuated by aminooxyacetic acid or L-aspartate (CAT inhibitors), iberiotoxin (large-conductance calcium-activated K+ channel blocker), TRAM-34 plus apamin (intermediate- and small-conductance Ca2+-activated K+ channel blockers) or glibenclamide (ATP-sensitive K+ channel blocker). 3-MPST and mitochondrial CAT were found in endothelial and smooth muscle cells while cytosolic CAT was located only in endothelial cells. Acetylcholine significantly increased the H2S levels. The H2S donor, NaHS, increased eNOS phosphorylation and down-regulated PDE5A.

Conclusions

Human conduit artery endothelium releases H2S under basal and stimulated conditions, involving the 3-MPST/CAT pathway, eNOS phosphorylation, PDE5A activity, and potassium channels. These findings may provide new therapeutic targets for treating vasospasm in CABG grafts and facilitate the development of new vasodilator drugs.

GABAA receptor, KATP channel and L-type Ca2+ channel is associated with facilitation effect of H2S on the baroreceptor reflex in spontaneous hypertensive rats

BACKGROUND

We aimed to investigate whether the facilitating effect of H₂S on the baroreceptor reflex is associated with the GABA_A receptor, K_ATP channel and L-type Ca²⁺ channel pathway.

METHODS

Spontaneously hypertensive rats (SHRs) and Wistar Kyoto (WKY) rats were used to investigate the facilitating effect of H₂S on the baroreceptor reflex by perfusing the isolated carotid sinus. The mechanism by which H₂S facilitated the baroreceptor reflex was determined by using Bay K8644 (an agonist of calcium channels), glibenclamide (Gli, a K_ATP channel blocker), and picrotoxin (PIC, a blocker of γ-aminobutyric acid [GABA]_A receptor).

RESULTS

As compared with WKY rats, SHRs showed impaired baroreceptor reflex sensitivity, as demonstrated by a right and upward shift of the functional curve for the intrasinus pressure-arterial blood pressure relation. H₂S perfusion (25, 50, or 100 μmol/L) dose-dependently ameliorated the impaired sensitivity of the baroreceptor reflex. Bay K8644 (500 nmol/L), Gli (20 μmol/L) and PIC (50 μmol/L) all prevented H₂S ameliorating the impaired baroreceptor reflex.

CONCLUSIONS

H₂S facilitating the baroreceptor reflex might be associated with activating the GABA_A receptor, opening the K_ATP channel, and closing the L-type Ca²⁺ channel. These areas should provide new targets for preventing and treating hypertension.

Simultaneous Measurements of Tension and Free H2S in Mesenteric Arteries

Hydrogen sulfide (H₂S), in addition to nitric oxide and carbon monoxide, is the third gasotransmitter and known to cause relaxation in peripheral arteries. Here we describe a method that allows simultaneous measurement of contractility in arteries mounted in an isometric wire myograph and the concentration of free H₂S in the lumen of the artery as well as in the organ bath. This method can be used to directly correlate how much free H₂S is needed to cause relaxation, which previously has been difficult to answer as H₂S can be found in many different forms.

Cystathionine γ-Lyase-Produced Hydrogen Sulfide Controls Endothelial NO Bioavailability and Blood Pressure

Hydrogen sulfide (H₂S) and NO are important gasotransmitters, but how endogenous H₂S affects the circulatory system has remained incompletely understood. Here, we show that CTH or CSE (cystathionine γ-lyase)-produced H₂S scavenges vascular NO and controls its endogenous levels in peripheral arteries, which contribute to blood pressure regulation. Furthermore, eNOS (endothelial NO synthase) and phospho-eNOS protein levels were unaffected, but levels of nitroxyl were low in CTH-deficient arteries, demonstrating reduced direct chemical interaction between H₂S and NO. Pretreatment of arterial rings from CTH-deficient mice with exogenous H₂S donor rescued the endothelial vasorelaxant response and decreased tissue NO levels. Our discovery that CTH-produced H₂S inhibits endogenous endothelial NO bioavailability and vascular tone is novel and fundamentally important for understanding how regulation of vascular tone is tailored for endogenous H₂S to contribute to systemic blood pressure function.

Mercaptopyruvate acts as endogenous vasodilator independently of 3-mercaptopyruvate sulfurtransferase activity

Hydrogen sulfide (H₂S) is produced by the action of cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) or 3-mercaptopyruvate sulfurtransferase (3-MST). 3-MST converts 3-mercaptopyruvate (MPT) to H₂S and pyruvate. H₂S is recognized as an endogenous gaseous mediator with multiple regulatory roles in mammalian cells and organisms. In the present study we demonstrate that MPT, the endogenous substrate of 3-MST, acts also as endogenous H₂S donor. Colorimetric, amperometric and fluorescence based assays demonstrated that MPT releases H₂S in vitro in an enzyme-independent manner. A functional study was performed on aortic rings harvested from C57BL/6 (WT) or 3-MST-knockout (3-MST^-/-) mice with and without endothelium. MPT relaxed mouse aortic rings in endothelium-independent manner and at the same extent in both WT and 3-MST^-/- mice. N5-(1-Iminoethyl)-l-ornithine dihydrochloride (L-NIO, an inhibitor of endothelial nitric oxide synthase) as well as 1H-[1,2,4]oxadiazolo [4,3-a]quinoxalin-1-one (ODQ, a soluble guanylyl cyclase inhibitor) did not affect MPT relaxant action. Conversely, hemoglobin (as H₂S scavenger), as well as glybenclamide (an ATP-dependent potassium channel blocker) markedly reduced MPT-induced relaxation. The functional data clearly confirmed a non enzymatic vascular effect of MPT. In conclusion, MPT acts also as an endogenous H₂S donor and not only as 3-MST substrate. MPT could, thus, be further investigated as a means to increase H₂S in conditions where H₂S bioavailability is reduced such as hypertension, coronary artery disease, diabetes or urogenital tract disease.

Vasoconstriction triggered by hydrogen sulfide: Evidence for Na+,K+,2Cl-cotransport and L-type Ca2+ channel-mediated pathway

Objectives

This study examined the dose-dependent actions of hydrogen sulfide donor sodium hydrosulphide (NaHS) on isometric contractions and ion transport in rat aorta smooth muscle cells (SMC).

Methods

Isometric contraction was measured in ring aortas segments from male Wistar rats. Activity of Na⁺/K⁺-pump and Na⁺,K⁺,2Cl^-cotransport was measured in cultured endothelial and smooth muscle cells from the rat aorta as ouabain-sensitive and ouabain-resistant, bumetanide-sensitive components of the ⁸⁶Rb influx, respectively.

Results

NaHS exhibited the bimodal action on contractions triggered by modest depolarization ([K⁺]_o=30 mM). At 10^-4 M, NaHS augmented contractions of intact and endothelium-denuded strips by ~ 15% and 25%, respectively, whereas at concentration of 10^-3 M it decreased contractile responses by more than two-fold. Contractions evoked by 10^-4 M NaHS were completely abolished by bumetanide, a potent inhibitor of Na⁺,K⁺,2Cl^-cotransport, whereas the inhibition seen at 10^-3 M NaHS was suppressed in the presence of K⁺ channel blocker TEA. In cultured SMC, 5×10^-5 M NaHS increased Na⁺,K⁺,2Cl^- - cotransport without any effect on the activity of this carrier in endothelial cells. In depolarized SMC, ⁴⁵Ca influx was enhanced in the presence of 10^-4 M NaHS and suppressed under elevation of [NaHS] up to 10^-3 M. ⁴⁵Ca influx triggered by 10^-4 M NaHS was abolished by bumetanide and L-type Ca²⁺ channel blocker nicardipine.

Conclusions

Our results strongly suggest that contractions of rat aortic rings triggered by low doses of NaHS are mediated by activation of Na⁺,K⁺,2Cl^-cotransport and Ca²⁺ influx via L-type channels.

The mechanism of action and role of hydrogen sulfide in the control of vascular tone

Our knowledge about hydrogen sulfide (H₂S) significantly changed over the last two decades. Today it is considered as not only a toxic gas but also as a gasotransmitter with diverse roles in different physiological and pathophysiological processes. H₂S has pleiotropic effects and its possible mechanisms of action involve (1) a reversible protein sulfhydration which can alter the function of the modified proteins similar to nitrosylation or phosphorylation; (2) direct antioxidant effects and (3) interaction with metalloproteins. Its effects on the human cardiovascular system are especially important due to the high prevalence of hypertension and myocardial infarction. The exact molecular targets that affect the vascular tone include the K_ATP channel, the endothelial nitric oxide synthase, the phosphodiesterase of the vascular smooth muscle cell and the cytochrome c oxidase among others and the combination of all these effects lead to the final result on the vascular tone. The relative role of each effect depends immensely on the used concentration and also on the used donor molecules but several other factors and experimental conditions could alter the final effect. The aim of the current review is to give a comprehensive summary of the current understanding on the mechanism of action and role of H₂S in the regulation of vascular tone and to outline the obstacles that hinder the better understanding of its effects.

Gasotransmitter Heterocellular Signaling

SIGNIFICANCE

The family of gasotransmitter molecules, nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S), has emerged as an important mediator of numerous cellular signal transduction and pathophysiological responses. As such, these molecules have been reported to influence a diverse array of biochemical, molecular, and cell biology events often impacting one another. Recent Advances: Discrete regulation of gasotransmitter molecule formation, movement, and reaction is critical to their biological function. Due to the chemical nature of these molecules, they can move rapidly throughout cells and tissues acting on targets through reactions with metal groups, reactive chemical species, and protein amino acids.

CRITICAL ISSUES

Given the breadth and complexity of gasotransmitter reactions, this field of research is expanding into exciting, yet sometimes confusing, areas of study with significant promise for understanding health and disease. The precise amounts of tissue and cellular gasotransmitter levels and where they are formed, as well as how they react with molecular targets or themselves, all remain poorly understood.

FUTURE DIRECTIONS

Elucidation of specific molecular targets, characteristics of gasotransmitter molecule heterotypic interactions, and spatiotemporal formation and metabolism are all important to better understand their true pathophysiological importance in various organ systems. Antioxid. Redox Signal. 26, 936-960.

H2S causes contraction and relaxation of major arteries of the rabbit

OBJECTIVE

Cardiovascular disease (CVD) caused by atherosclerosis remains a worldwide burden. Hydrogen sulfide is a promising new therapeutic avenue for the treatment of CVD, however reports show exogenous H₂S has both vasodilator and vasoconstrictor effects depending on organ examined, and in vitro studies in animal models which are not resistant to developing atherosclerosis are limited. We sought to determine if rabbit arteries constricted or dilated to hydrogen sulfide.

MATERIAL AND METHODS

The aorta, carotid, renal and iliac arteries were harvested from New Zealand White rabbits (n=4) and subjected to a concentration response curve to the fast H₂S releaser NaHS. In addition, a bolus dose of NaHS was used to determine if further dilation was achievable after maximum dilation to acetylcholine similar to nitric oxide donors. Further, NaHS was used to determine if H₂S could impair homocysteine induced endothelial dysfunction.

RESULTS

Blood vessels relaxed poorly to NaHS and contracted at higher doses. A bolus dose of NaHS relaxed then contracted the aorta, however a bolus dose of NaHS after maximal relaxation to acetylcholine caused marked contraction. NaHS did not prevent homocysteine induced vascular dysfunction.

CONCLUSION

NaHS at low doses caused minor relaxation of rabbit blood vessels, indicating a possible therapeutic benefit for low dose H₂S in the cellular milieu.

Hydrogen sulfide attenuates gastric mucosal injury induced by restraint water-immersion stress via activation of KATP channel and NF-κB dependent pathway

AIM

To explore the effect of hydrogen sulfide (H₂S) on restraint water-immersion stress (RWIS)-induced gastric lesions in rats and the influence of adenosine triphosphate (ATP)-sensitive potassium (K_ATP) channels and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway on such an effect.

METHODS

Male Wistar rats were randomly divided into a control group, a physiological saline (PS) group, a sodium hydrosulfide (NaHS) group, a glibenclamide (Gl) group, Gl plus NaHS group, a pyrrolidine dithiocarbamate (PDTC) group, and a PDTC plus NaHS group. Gastric mucosal injury was induced by RWIS for 3 h in rats, and gastric mucosal damage was analyzed after that. The PS, NaHS (100 μmol/kg body weight), Gl (100 μmol/kg body weight), Gl (100 μmol/kg or 150 μmol/kg body weight) plus NaHS (100 μmol/kg body weight), PDTC (100 μmol/kg body weight), and PDTC (100 μmol/kg body weight) plus NaHS (100 μmol/kg body weight) were respectively injected intravenously before RWIS.

RESULTS

RWIS induced serious gastric lesions in the rats in the PS pretreatment group. The pretreatment of NaHS (a H₂S donor) significantly reduced the damage induced by RWIS. The gastric protective effect of the NaHS during RWIS was attenuated by PDTC, an NF-κB inhibitor, and also by glibenclamide, an ATP-sensitive potassium channel blocker, in a dose-dependent manner.

CONCLUSION

These results suggest that exogenous H₂S plays a protective role against RWIS injury in rats, possibly through modulation of K_ATP channel opening and the NF-κB dependent pathway.

Characterization of relaxant mechanism of H2 S in mouse corpus cavernosum

The aim of this study was to investigate the mechanism of H2 S-induced relaxation in mouse corpus cavernosal tissue. l-cysteine (10(-6) × 10(-3) mol/L) and exogenous H2 S (NaHS; 10(-6) to 10(-3) mol/L) induced concentration-dependent relaxation. l-cysteine-induced relaxations was reduced by d,l-propargylglycine, a cystathionine gamma lyase (CSE) inhibitor but not influenced by aminooxyacetic acid, a cystathionine beta synthase (CBS) inhibitor. l-cysteine induced relaxations, but not of those of H2 S diminished in endothelium-denuded tissues. N(ω) -nitro-l-arginine (l-NA; 10(-4) mol/L), a nitric oxide synthase inhibitor, and ODQ (10(-4) mol/L), a guanylyl cyclase inhibitor, increased the H2 S-induced relaxation. Zaprinast (5 × 10(-6) mol/L) and sildenafil (10(-6) mol/L), phosphodiesterase inhibitors, inhibited H2 S-induced relaxation. Adenylyl cyclase inhibitors N-ethylmaleimide (2.5 × 10(-5) mol/L) and SQ22536 (10(-4) mol/L) reduced relaxation to H2 S. Also, H2 S-induced relaxation was reduced by KCl (50 mmol/L), 4-aminopyridine (10(-3) mol/L), a Kv inhibitor, glibenclamide (10(-5) mol/L), a KATP inhibitor or barium chloride (10(-5) mol/L), a KIR inhibitor. However, H2 S-induced relaxation was not influenced by apamin (10(-6) mol/L), a SKC a (2+) inhibitor, charybdotoxin (10(-7) mol/L), an IKC a (2+) and BKC a (2+) inhibitor or combination of apamin and charybdotoxin. Nifedipine (10(-6) mol/L), an L-type calcium channel blocker and atropine (10(-6) mol/L), a muscarinic receptor blocker, inhibited H2 S-induced relaxation. However, H2 S-induced relaxation was not influenced by ouabain (10(-4) mol/L), a Na(+) /K(+) -ATPase inhibitor. This study suggests that H2 S endogenously synthesizes from l-cysteine by CSE endothelium-dependent in mouse corpus cavernosum tissue, and exogenous H2 S may cause endothelium-independent relaxations via activation of K channels (KATP channel, KV channels, KIR channels), L-type voltage-gated Ca(2+) channels, adenylyl cyclase/cAMP pathway and muscarinic receptor, and there is the interaction between H2 S and NO/cGMP.

Functional promoter polymorphisms direct the expression of cystathionine gamma-lyase gene in mouse models of essential hypertension

Despite the well-known role of cystathionine γ-lyase (Cth) in cardiovascular pathophysiology, transcriptional regulation of Cth remains incompletely understood. Sequencing of the Cth promoter region in mouse models of genetic/essential hypertension (viz. Blood Pressure High [BPH], Blood Pressure Low [BPL] and Blood Pressure Normal [BPN] mice) identified several genetic variations. Transient transfections of BPH/BPL-Cth promoter-reporter plasmids into various cell types revealed higher promoter activity of BPL-Cth than that of BPH-Cth. Corroboratively, endogenous Cth mRNA levels in kidney and liver tissues were also elevated in BPL mice. Computational analysis of the polymorphic Cth promoter region predicted differential binding affinity of c-Rel, HOXA3 and IRF1 with BPL/BPH-Cth promoter domains. Over-expression of c-Rel/HOXA3/IRF1 modulated BPL/BPH-Cth promoter activities in a consistent manner. Gel shift assays using BPH/BPL-Cth-promoter oligonucleotides with/without binding sites for c-Rel/HOXA3/IRF1 displayed formation of specific complexes with c-Rel/HOXA3/IRF1; addition of antibodies to reaction mixtures resulted in supershifts/inhibition of Cth promoter-transcription factor complexes. Furthermore, chromatin immunoprecipitation (ChIP) assays proved differential binding of c-Rel, HOXA3 and IRF1 with the polymorphic promoter region of BPL/BPH-Cth. Tumor necrosis factor-α (TNF-α) reduced the activities of BPL/BPH-Cth promoters to different extents that were further declined by ectopic expression of IRF1; on the other hand, siRNA-mediated down-regulation of IRF1 rescued the TNF-α-mediated suppression of the BPL/BPH-Cth promoter activities. In corroboration, ChIP analysis revealed enhanced binding of IRF1 with BPH/BPL-Cth promoter following TNF-α treatment. BPL/BPH-Cth promoter activity was diminished upon exposure of hepatocytes and cardiomyoblasts to ischemia-like pathological condition due to reduced binding of c-Rel with BPL/BPH-Cth-promoter. Taken together, this study reveals the molecular basis for the differential expression of Cth in mouse models of essential hypertension under basal and pathophysiological conditions.

Vasodilator activity of hydrogen sulfide (H2S) in human mesenteric arteries

The role of endogenous H₂S has been highlighted as a gaseous transmitter. The vascular smooth muscle inhibitory effects of H₂S have been characterized in isolated aorta and mesenteric arteries in rats and mice. Our study was aimed at investigating the vascular effects of H₂S on human isolated mesenteric arteries and examining the underlying mechanisms involved. All experiments were performed on rings (4-8mm long) of human mesenteric arteries obtained from patients undergoing abdominal surgery. Ethical approval was obtained from the Ethics Committee of the University Hospital of the University of Florence (app. N. 2015/0024947). The effect of NaHS, an H₂S donor, was determined using noradrenaline pre-contracted human isolated mesenteric rings. NaHS evoked a concentration-dependent relaxation (EC₅₀ 57μM). In contrast, homocysteine, an endogenous precursor of H₂S, failed to affect human isolated mesenteric rings. Vasorelaxant response to NaHS was reduced by endothelium removal, application of the nitric oxide synthase inhibitor L-NAME and ODQ inhibitor of cyclic GMP. SQ 22536, an adenylate-cyclase inhibitor, failed to block NaHS-induced vasorelaxation. Inhibition of endogenous prostanoid production by indomethacin significantly reduced NaHS induced vasorelaxation. The role of potassium channels was also examined: blockers of the Ca²⁺-dependent potassium channel, charybdotoxin and apamin, failed to have any influence on the relaxant response to NaHS on this vascular tissue. In summary, H₂S induced relaxation of isolated rings of human mesenteric arteries. Endothelium-dependent related mechanisms with the stimulation of ATP-sensitive potassium channels represents important cellular mechanisms for H₂S effect on human mesenteric arteries.

Effect of exogenous hydrogen sulfide on gastric acid secretion

BACKGROUND AND AIM

H2 S is an important gasotransmitter in the gastrointestinal tract. The aim of the present study was to investigate the effect of exogenous H2 S on gastric acid secretion.

METHODS

Male Wistar rats were randomly divided into physiological saline (PS) group, sodium hydrosulfide (NaHS; 50, 100, and 150 µmol/kg body weight) group, glibenclamide + NaHS group, and SQ22536 + NaHS group. PH of gastric juice before injection and after injection were determined by a PH meter.

RESULTS

The results showed that NaHS, an exogenous H2 S donor, injected into the enterocoelia significantly reduced the PH of gastric juice, the same volume of PS administered similarly did not change PH of gastric juice, the promotional effect of NaHS on gastric acid secretion could be abolished by glibenclamide, an ATP-sensitive potassium channel K(ATP) blocker SQ22536, an inhibitor of adenyl cyclase.

CONCLUSIONS

The data from these experiments suggest that exogenous H2 S promoted gastric acid secretion, which may occur via K(ATP) channels and activate AC-cAMP pathway.

Reverse Regulatory Pathway (H2S / PGE2 / MMP) in Human Aortic Aneurysm and Saphenous Vein Varicosity

Hydrogen sulfide (H₂S) is a mediator with demonstrated protective effects for the cardiovascular system. On the other hand, prostaglandin (PG)E₂ is involved in vascular wall remodeling by regulating matrix metalloproteinase (MMP) activities. We tested the hypothesis that endogenous H₂S may modulate PGE₂, MMP-1 activity and endogenous tissue inhibitors of MMPs (TIMP-1/-2). This regulatory pathway could be involved in thinning of abdominal aortic aneurysm (AAA) and thickening of saphenous vein (SV) varicosities. The expression of the enzyme responsible for H₂S synthesis, cystathionine-γ-lyase (CSE) and its activity, were significantly higher in varicose vein as compared to SV. On the contrary, the endogenous H₂S level and CSE expression were lower in AAA as compared to healthy aorta (HA). Endogenous H₂S was responsible for inhibition of PGE₂ synthesis mostly in varicose veins and HA. A similar effect was observed with exogenous H₂S and consequently decreasing active MMP-1/TIMP ratios in SV and varicose veins. In contrast, in AAA, higher levels of PGE₂ and active MMP-1/TIMP ratios were found versus HA. These findings suggest that differences in H₂S content in AAA and varicose veins modulate endogenous PGE₂ production and consequently the MMP/TIMP ratio. This mechanism may be crucial in vascular wall remodeling observed in different vascular pathologies (aneurysm, varicosities, atherosclerosis and pulmonary hypertension).

Perfusion of Isolated Carotid Sinus With Hydrogen Sulfide Attenuated the Renal Sympathetic Nerve Activity in Anesthetized Male Rats

The purpose of the present study was to define the indirect central effect of hydrogen sulfide (H2S) on baroreflex control of sympathetic outflow. Perfusing the isolated carotid sinus with sodium hydrosulfide (NaHS), a H2S donor, the effect of H2S was measured by recording changes of renal sympathetic nerve activity (RSNA) in anesthetized male rats. Perfusion of isolated carotid sinus with NaHS (25, 50, 100 μmol/l) dose and time-dependently inhibited sympathetic outflow. Preconditioning of glibenclamide (20 µmol/l), a ATP-sensitive K+ channels (KATP) blocker, the above effect of NaHS was removed. With 1, 4-dihydro-2, 6-dimethyl-5-nitro-4-(2-[trifluoromethyl] phenyl) pyridine-3-carboxylic acid methyl ester (Bay K8644, 500 nmol/l) pretreatment, which is an agonist of L-calcium channels, the effect of NaHS was eliminated. Perfusion of cystathionine γ-lyase (CSE) inhibitor, DL-propargylglycine (PPG, 200 μmol/l), increased sympathetic outflow. The results show that exogenous H2S in the carotid sinus inhibits sympathetic outflow. The effect of H2S is attributed to opening KATP channels and closing the L-calcium channels.

Hydrogen sulfide: A novel nephroprotectant against cisplatin-induced renal toxicity

Cisplatin is a potent chemotherapeutic agent for the treatment of various solid-organ cancers. However, a plethora of evidence indicates that nephrotoxicity is a major side effect of cisplatin therapy. While the antineoplastic action of cisplatin is due to formation of cisplatin-DNA cross-links, which damage rapidly dividing cancer cells upon binding to DNA, its nephrotoxic effect results from metabolic conversion of cisplatin into a nephrotoxin and production of reactive oxygen species, causing oxidative stress leading to renal tissue injury and potentially, kidney failure. Despite therapeutic targets in several pre-clinical and clinical studies, there is still incomplete protection against cisplatin-induced nephrotoxicity. Hydrogen sulfide (H2S), the third discovered gasotransmitter next to nitric oxide and carbon monoxide, has recently been identified in several in vitro and in vivo studies to possess specific antioxidant, anti-inflammatory and anti-apoptotic properties that modulate several pathogenic pathways involved in cisplatin-induced nephrotoxicity. The current article reviews the molecular mechanisms underlying cisplatin-induced nephrotoxicity and displays recent findings in the H2S field that could disrupt such mechanisms to ameliorate cisplatin-induced renal injury.

Cross talk between polysulfide and nitric oxide in rat peritoneal mast cells

The aim of this study was to define the effects of polysulfide on intracellular Ca(2+) concentration ([Ca(2+)]i) and the underlying machinery, especially from the hydrogen sulfide (H2S) and nitric oxide (NO) perspectives, in rat peritoneal mast cells. We found that a polysulfide donor, Na2S4, increased [Ca(2+)]i, which is both extracellular and intracellular Ca(2+) dependent. Intracellular Ca(2+) release induced by Na2S4 was attenuated by the addition of a ryanodine receptor blocker. A slow-releasing H2S donor, GYY4137, dose dependently increased [Ca(2+)]i that was independent from extracellular Ca(2+) influx. The GYY4137-induced [Ca(2+)]i release was partially attenuated in the presence of the ryanodine receptor blocker. Both polysulfide and H2S donors increased the intracellular NO levels in DAF-2-loaded mast cells, which were abolished by an NO scavenger, cPTIO. Inhibition of NO synthase (NOS) significantly abolished the polysulfide- or H2S-donor-induced [Ca(2+)]i elevation in the absence of extracellular Ca(2+) An NO donor, diethylamine (DEA) NONOate, increased [Ca(2+)]i in a concentration-dependent manner, in which both extracellular and intracellular Ca(2+) are associated. At higher concentrations, the DEA NONOate-induced [Ca(2+)]i increases were attenuated in the absence of extracellular Ca(2+) and by the addition of the ryanodine receptor blocker. H2S and NO dose dependently induced polysulfide production. Curiously, polysulfide, H2S, and NO donors had no effect on mast cell degranulation. Among synthases, cystathionine-γ-lyase, and neuronal NOS seemed to be the major H2S- and NO-producing synthases, respectively. These results indicate that polysulfide acts as a potential signaling molecule that regulates [Ca(2+)]i homeostasis in rat peritoneal mast cells via a cross talk with NO and H2S.

H2S induces vasoconstriction of rat cerebral arteries via cAMP/adenylyl cyclase pathway

Hydrogen sulfide (H2S), traditionally known for its toxic effects, is now involved in regulating vascular tone. Here we investigated the vasoconstrictive effect of H2S on cerebral artery and the underlying mechanism. Sodium hydrosulfide (NaHS), a donor of H2S, concentration-dependently induced vasoconstriction on basilar artery, which was enhanced in the presence of isoprenaline, a β-adrenoceptor agonist or forskolin, an adenylyl cyclase activator. Administration of NaHS attenuated the vasorelaxant effects of isoprenaline or forskolin. Meanwhile, the NaHS-induced vasoconstriction was diminished in the presence of 8B-cAMP, an analog of cAMP, but was not affected by Bay K-8644, a selective L-type Ca(2+) channel agonist. These results could be explained by the revised effects of NaHS on isoprenaline-induced cAMP elevation and forskolin-stimulated adenylyl cyclase activity. Additionally, NaHS-induced vasoconstriction was enhanced by removing the endothelium or in the presence of L-NAME, an inhibitor of nitric oxide synthase. L-NAME only partially attenuated the effect of NaHS which was given together with forskolin on the pre-contracted artery. In conclusion, H2S induces vasoconstriction of cerebral artery via, at least in part, cAMP/adenylyl cyclase pathway.

Hydrogen sulphide-induced relaxation of porcine peripheral bronchioles

BACKGROUND AND PURPOSE

Hydrogen sulphide (H2S) is an endogenous gasotransmitter. Although it has been shown to elicit responses in vascular and other smooth muscle preparations, a role for endogenously produced H2S in mediating airway tone has yet to be demonstrated. Therefore, the aim of this study was to determine whether H2S is produced within the airways and to determine the functional effect on airway tone.

EXPERIMENTAL APPROACH

Small peripheral airways (<5 mm in diameter) from porcine lungs were set up in isolated tissue baths, pre-contracted with the muscarinic agonist carbachol, and then exposed to either the H2S donor sodium hydrosulphide (NaHS), or the precursor L-cysteine. H2S production from L-cysteine or 3-mercaptopyruvate in tissue homogenates was measured by the methylene blue assay. Expression of the H2S-synthesizing enzymes cystathionine β-synthase (CBS), cystathionine γ lyase (CSE) and 3-mercaptopyruvate sulphurtransferase (3-MST) were measured by Western blotting.

KEY RESULTS

NaHS caused a large relaxation of the airways, which was inhibited partially by pre-contraction with KCl or exposure to tetraethylammonium, but not glibenclamide, paxilline or 4-aminopyridine. L-cysteine also caused a relaxation of the airways which was inhibited by the CBS inhibitor aminooxyacetic acid. Tissue homogenates from airways exposed to L-cysteine or 3-mercaptopyruvate in vitro showed a significant production of H2S. Western blotting demonstrated immunoreactivity to CBS, CSE and 3-MST enzymes in the airways.

CONCLUSIONS AND IMPLICATIONS

These data demonstrate that H2S can be produced endogenously within porcine airways causing relaxation. The mechanism of relaxation depends, in part, on K(+) channel activity.